CRM-15578 - CRM_Core_Transaction - Add support for nested transactions; add tests.
CRM-15578 - APIv3 - options.force_rollback
CRM_Core_TransactionTest - Improve reporting of unplanned exceptions
CRM-15578, CRM-13523 - CiviUnitTestCase - Improve output for PEAR DB errors
Merge pull request #4548 from totten/master-savepoints

CRM-15578 - CRM_Core_Transaction - Add support for nested transactions (savepoints)